I'm porting my HPFS driver to 2.3.18 and I don't know how to write
get_block properly. When user does lseek(far beyond file end) and
write(), get_block must allocate a lot of sectors and clear them (HPFS
doesn't support holes). The question is: what call should I use to
clear these sectors?
Using bread/mark_buffer_dirty/brelse is bad idea - when the block is
read to page cache later, there are two buffers pointing to the same block
=> data corruption.
Calling page cache functions to create buffers? get_block is called from
page cache layer, thus calling anything from there makes possible deadlock
condition.
Modifying page cache directly ... black magic.
What should I do with it? Is there any function that I didn't notice? Of
course I could write routines to directly touch page cache and attach
buffer there, but I think it's dirty. Especially when other filesystem
also need to do the same (fat currently crashes when writing beyond file
end, other filesystems aren't ported yet)
Mikulas Patocka
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